Method and apparatus for waking remote terminal

ABSTRACT

A method and apparatus for waking up a remote main system. The method includes: certifying whether a user of a terminal which transmits a packet for waking up a main system that is in a sleeping state is a legitimate user of the main system; and transmitting a wake-up signal to the main system if it is certified that the user is legitimate. Access of uncertified users can be prevented by certifying a user who is in the process of logging on or logging into the main system before the main system wakes up.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of Korean Patent Application No.10-2004-0022031, filed on Mar. 31, 2004, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for controllingthe power consumption of terminal in a network, and more particularly,to a method and apparatus for driving a remote terminal.

2. Description of Related Art

The energy star program of the US government, announced in 1963, limitsthe power consumption of a personal computer when not in use, and the USgovernment prohibits the sale of any product not manufactured accordingto this standard. PC manufacturers have developed products to followthis standard. However, with the development of networks, which connectPCs to each other, a need has arisen for network administrators toupdate software through the network or carry out data back up whileusers are away from their PCs. To perform such operations the PC must bein a normal state, and to achieve this a so-called “magic packet” thatcan wake up a remote terminal from a sleeping state has been proposed.

FIG. 1 is a diagram illustrating the format of a conventional magicpacket.

Referring to FIG. 1, the magic packet includes an Ethernet header, asynchronization field, a magic packet discriminating field, and otherfields. The magic packet is an Ethernet frame and follows the Ethernetstandard.

A person who wants access to a remote terminal creates a magic packet asshown in FIG. 1 and transmits the magic packet to the remote terminal.The remote terminal receives the magic packet and compares a destinationaddress, which is recorded on a destination address field of theEthernet header of the received magic packet, with its own address. Ifthe addresses match, the magic packet is processed according to a magicpacket processing method.

To be more specific, first of all it is checked whether the valuerecorded on the synchronization field is FF repeated six times. If thiscondition is satisfied, it is checked whether the value recorded on themagic packet discriminating field is the media access control (MAC)address of a remote terminal repeated sixteen times. If this conditionis also satisfied, then a wake-up signal is transmitted to the mainsystem that is in a sleeping state. The main system, which receives thewake-up signal, wakes up by booting up.

However, since an arbitrary user can wake-up a sleeping remote terminalwith a magic packet, without the user of the remote terminal beingaware, a malicious user can retrieve information stored in the remoteterminal or carry out other damaging operations.

In addition, since the magic packet is processed in the link layer usingonly the MAC address, services provided by higher layers such as thenetwork layer cannot be used. For example, routing services, provided bya router that configures the transmission pathway of a packet on thebasis of the IP address, cannot be used.

BRIEF SUMMARY

An aspect of the present invention provides a method and apparatus inwhich a process of logging on or logging into a main system, which isperformed for user certification, is performed before the main systemwakes up so as to block access of an uncertified user.

An aspect of the present invention also provides a method and apparatusfor providing services based on upper layer information by incorporatingthe higher class information in addition to link layer information intoa main system wake-up packet.

According to an aspect of the present invention, there is provided amethod of waking up a main system, including: certifying whether a userof a terminal which transmits a packet for waking up a main system in asleeping state is a legitimate user of the main system; and transmittinga wake-up signal to the main system when it is certified that the useris legitimate.

According to another aspect of the present invention, there is providedan apparatus for waking up a main system, including: a certifying unitwhich certifies whether a user of a terminal which transmits a packet towake up a main system in a sleeping state is a legitimate user; and acontrol unit which transmits a drive signal to the main system when thecertifying unit confirms that the user is a legitimate user.

According to another aspect of the present invention, there is provideda method of transmitting higher layer information, including: storingthe higher layer information included in a packet for waking up a mainsystem in a sleeping state; and transmitting the higher layerinformation to the main system that is woken up by the packet. Thehigher layer information is information of layers at least as high as anetwork layer.

According to another aspect of the present invention, there is provideda communication method including: requesting via a host to wake up aremote terminal in a sleeping state; certifying whether a user of thehost is a legitimate user of the remote terminal; waking up the remoteterminal when it is confirmed that the user is a legitimate user; andcommunicating between the host and the remote terminal which is wokenup.

According to another aspect of the present invention, there is provideda computer readable medium having embodied thereon a computer programfor the above-described method of waking up a main system.

According to anther aspect of the present invention, there is provided acomputer readable medium having embodied thereon a computer program forthe above-described method of transmitting higher layer information.

According to another aspect of the preset invention, there is provided acomputer readable medium having embodied thereon a computer program forthe above-described communication method.

Additional and/or other aspects and advantages of the present inventionwill be set forth in part in the description which follows and, in part,will be obvious from the description, or may be learned by practice ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present invention willbecome apparent and more readily appreciated from the following detaileddescription, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a diagram illustrating the format of a conventional magicpacket;

FIG. 2 is a diagram illustrating the structure of a PC according to anembodiment of the present invention;

FIG. 3 illustrates the formats of wake-up packets according to anembodiment of the present invention;

FIG. 4 is a diagram illustrating the structure of a first communicationsystem according to an embodiment of the present invention;

FIG. 5 is a flowchart of a first communication method according to anembodiment of the present invention;

FIG. 6 is a flowchart of a method of waking up a first main systemaccording to an embodiment of the present invention;

FIG. 7 is a diagram illustrating the structure of a second communicationsystem according to an embodiment of the present invention;

FIG. 8 is a flowchart of a second communication method according to anembodiment of the present invention;

FIG. 9 is a flowchart illustrating a method of waking up a second mainsystem when a packet is transmitted according an embodiment of thepresent invention;

FIG. 10 is a flowchart illustrating a method of waking up the secondmain system when a packet is received according to an embodiment of thepresent invention;

FIG. 11 is a diagram of a structure of a third communication systemaccording to an embodiment of the present invention;

FIG. 12 is a flowchart of a third communication method according to anembodiment of the present invention:

FIG. 13 is a flowchart illustrating a method of waking a third mainsystem when a packet is transmitted according to an embodiment of thepresent invention; and

FIG. 14 is a flowchart illustrating a method of waking up the third mainsystem when a packet is received according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures.

FIG. 2 is a diagram of the structure of a PC according to an embodimentof the present invention.

Referring to FIG. 2, a PC 1 includes a system wake-up apparatus 11, amain system 12, and a legacy network card 13. The PC according to thepresent invention can be a desktop computer connected to a wirednetwork, a lap-top computer, or a personal digital assistant (PDA)connected to a wireless network.

In addition to a basic input/output system (BIOS) 121, a powermanagement apparatus 122, and a protocol stack 123, the main system 12includes various other elements (not shown) of the PC 1 such as acentral processing unit (CPU), memory, and an input/output unit, etc.The legacy network card 13 and other parts of the PC 1 are of standardspecifications, and thus their description and/or depiction will beomitted.

The main system wake-up apparatus 11 is a sub-system of the main system12 and includes a bridge 111, a link layer processing unit 112, anetwork layer processing unit 113, a security engine 114, a storing unit115, a user certifying unit 116, and a control unit 117.

The bridge 111 receives a packet via an external network (not shown), asplitter 21, which is installed within home, and a modem 22. Thesplitter 21 separates a low frequency bandwidth signal to be transmittedto a phone 23 and a high frequency bandwidth signal to be transmitted tothe modem 22. The bridge 111 receives from the power managementapparatus 122 of the main system 12 main system state information onwhether the current state of the main system is a normal state in whichthe main system 12 is driven with a normal level of power or a sleepingstate (a standby condition for which low power is applied.

The bridge 111 transmits the received packet to the link layerprocessing unit 112 according to the received main system stateinformation when the main system 12 is in a sleeping state and transmitsthe received packet to the legacy network card 13 when the main system12 is in a normal state. Therefore, when the main system 12 is in anormal state, the legacy network card 13 receives the packet andprocesses the received packet as a normal packet. When the main system12 is in a sleeping state, the link layer processing unit 112 receivesthe packet and processes the received packet using a method according tothe present embodiment.

FIG. 3 is a diagram illustrating the formats of wake-up packetsaccording to an embodiment of the present invention.

Referring to FIG. 3, wake-up packets 31 and 32 include not only linklayers 311 and 315 but also network layers 312, 313, and 314, which arehigher layers than the link layers, unlike the magic packet illustratedin FIG. 1. In addition, the network layers 312, 313, and 314 includepayload 314 secured according to internet protocol security protocol(IPsec).

Wake-up packets can be realized with various formats according tosecurity methods, such as a packet that employs an authentication header(AH) security method, as provided by IPsec, or a packet that employs anencapsulated security payload (ESP) security method, or a packet thatemploys both the AH security method and the ESP security method.

FIG. 3 illustrates a wake-up packet 31 that employs the AH securitymethod and a wake-up packet 32 that employs the ESP security method, asexamples. However, it is to be understood that other security methodsare both contemplated and possible.

The wake-up packet 31, which employs the AH security method, includes alink header 311, an IP header 312, a AH header 313, a payload 314, and alink trailer 315. The wake-up packet 32, which employs the ESP securitymethod, includes a link header 321, an IP header 322, an ESP header 323,a payload 324, an ESP trailer 325, an ESP certification 326, and a linktrailer 327.

In general, the link headers 311 and 321 are realized as magic packetssuch as an Ethernet header. In other words, the link headers 311 and 321include a destination address field, a sender address field, and a typefield. The MAC address of the terminal that is the destination of thepacket is recorded in the destination address field, and the MAC addressof the terminal which is the server of the packet is recorded in thesender address field. The MAC address is a 48-bit hardware address,allocated by the network card manufacturer, and each network card has aunique value. Referring to FIGS. 2 and 3, the main system wake-upapparatus 11 receives a packet in the place of the legacy network card13 when the PC 1 is in a sleeping state, and the main system wake-upapparatus 11 has an identical MAC address to the legacy network card 13.For this to be possible the main system wake-up apparatus 11 receivesthe MAC address from the legacy network card 13 and stores the receivedMAC address in the storing unit 115.

Information for discriminating the protocol of a packet, which isrecorded on a data region next to the link header, is recorded in thetype field. For example, if a packet recorded in the data region is anIPv6 packet type, then information indicating Ipv6 will be recorded inthe type field.

The IP headers 312 and 322 are realized as an IPv4 header or an IPv6header depending on the IP protocol version. In general, the IP headers312 and 322 include a destination address field, and a sender addressfield, etc. The IP address of the terminal that is the destination ofthe packet is recorded in the destination address field, and the IPaddress of the terminal that is the sender of the packet is recorded inthe sender address field. The IP address in the present embodiment canbe a fixed IP address or a dynamic IP address. When the IP address is adynamic IP address, the new IP address is stored in the storing unit 115of FIG. 2 whenever the IP address changes.

If the IP address is known even if the MAC address of the remoteterminal that should be woken up is not known, the wake-up packets 31and 32 shown in FIG. 3 can specify a remote terminal to be woken upusing the IP address, since they process the transceiving of the packetusing the IP address, unlike the magic packet shown in FIG. 1. In thiscase, a broadcast address is recorded in the destination address fieldof the link header. In other words, a user who knows the IP address butnot the MAC address of the PC 1 of FIG. 1 will record a broadcastaddress in the destination address field of the link header and transmitthe wake-up packets 31 and 32 on which the IP address of the PC 1 ofFIG. 2 is recorded to the destination address field of the IP header.The wake-up packets 31 and 32 are transmitted to all nodes on thenetwork in a broadcast method, and the PC 1 receives the wake-up packets31 and 32 and recognizes their destination referring to the IP addressthat is recorded in the destination field of the IP header of thereceived wake-up packets 31 and 32.

On the other hand, if the MAC address is known but the IP address of theremote terminal is not known, the remote terminal to be woken up shouldbe specified using a MAC address, as in the case of the magic packet. Inthis case, a broadcast address is recorded in the destination addressfield of the IP header.

The wake-up packets 31 and 32 include network layers, as opposed to themagic packets which include only the link layers. To confirm whichpacket is a wake-up packet, a protocol field of the IPv4 header or thenext header field of the IPv6 header is referred to as in other packets.The wake-up packets 31 and 32 each include a security application regionwhich is secured by an AH header 313 and/or an ESP header 323 asdescribed below. It is possible to confirm whether the packet is awake-up packet by checking whether a value which indicates the AH header313 and/or the ESP header 323 is recorded in the protocol field of theIpv4 header or the next header field of the Ipv6 header. Alternatively,a new value, which is not equal to the values of the protocol field andthe next heater field according to IPv4 or IPv6 standard, can bedesignated as a value that is indicative of a wake-up packet, which isan IP packet that is newly suggested in the present invention. In thiscase, it can be identified whether a packet is a wake-up packet or notby checking whether that value has been recorded.

The AH header 313 provides services such as the integrity of data andcertification of the sender. On the other hand, the ESP header 323provides services of not only the integrity of data and certification ofthe sender, but also confidentiality of data.

The payloads 314 and 324 are security application regions secured by theAH header 313 and the ESP header 324. User certification information isrecorded in the payloads 314 and 324. As described above, the wake-uppackets 31 and 32 have the same formats as general IP packets.Therefore, a router, which relays the wake-up packets 31 and 32 to thedestination terminal, can route the wake-up packets 31 and 32 withoutany additional steps, through the optimum path in a speedy manner,referring to the IP header of the wake-up packets 31 and 32. In otherwords, the bridge 111 can receive a packet that passes through theoptimum path determined by the router based on the IP address includedin the wake-up packets 31 and 32.

Referring to FIGS. 2 and 3, the link layer processing unit 112 examinesthe link headers 311 and 321 of the packets received from the bridge 111and processes the received packet according to the result. To be morespecific, the link layer processing unit 112 checks whether the MACaddress recorded in the destination address field of the link headermatches the MAC address stored in the storing unit 115, and when it isconfirmed that they match, the data region, that is the IP packet, isextracted from the received packet and is transmitted to the networklayer processing unit 113. If the value recorded in the destinationaddress field of the link header is broadcast, the IP packet must beextracted from the received packet and transmitted to the network layerprocessing unit 113.

The network layer processing unit 113 examines the IP header of the IPpacket received from the link layer processing unit 112 and processesthe received IP packet according to the result. To be more specific, ifthe IP address recorded in the destination address field of the IPheader matches the IP address stored in the storing unit 115, the typeof the received IP is confirmed. As described above, the confirmation iscarried out by referring to the value of the protocol field of the Ipv4or the next header field of the Ipv6 header. As a result when it isconfirmed that the packet is a wake-up packet the portion after the IPheader is processed according to a wake-up packet processing method, andwhen the packet is another type of packet, the portion after the IPheader is processed according to the packet type's processing method.

When the received IP packet is a response for the IP address request theIP address is extracted from the payload which is the portion after theIP header and is stored in the storing unit 115. When the received IPpacket is a packet for maintaining the connection with the proxy 3 thereceived packet is discarded without taking any other measures. When thereceived IP packet is a request for communication with the PC 1, aresponse which includes the IP address stored in the storing unit 115 istransmitted to the terminal which transmitted the communication request.When the received IP packet is a wake-up packet like 31 and 32, thenetwork layer processing unit 113 networks with a security engine 114 tocancel the security of the security application region by the AH header313 or the ESP header 314.

The security engine 114 calculates the integrity check value using thevalue of the fields of the IP packet according to a certificationalgorithm and compares the calculated value with the values recorded ina certification data field of the AH header 313 or the ESP header 314.As a result, when they match, access to the payloads 314 and 324 isgranted. In other words, the security of the security application regionis cancelled. The network layer processing unit 113 extracts usercertification information from the payloads 314 and 324 in whichsecurity is cancelled by the security engine 114.

The storing unit 115 stores the IP address of the main system 12, theMAC address of the legacy network card 13, and the user certificationinformation.

The user certifying unit 116 certifies whether the user of the terminalwhich transmitted the wake-up packets 31 and 32 is a legitimate user ofthe main system 12 based on the user certification information extractedby the network layer processing unit 113. The user certificationinformation allows logging on to the main system 12. Logging on is aprocess for receiving permission to use the operating system (OS) of aremote terminal or an application program. In a system using a unix OSthe term log-in is used instead of log-on. Currently, user IDs andpasswords are used as log-on or log-in information, but to strengthensecurity a user profile may be added.

Conventionally, the log-on process was carried out after the PC 1 waswoken from a sleeping state. However, in this case normal power has beenalready provided to the PC 1 before the log-on process, and a malicioususer can retrieve confidential information by penetrating the PC 1 orcarry out damaging operations without having to go through the log-onprocess. In the present embodiment, the log-on process is carried outbefore waking up the PC 1, thereby completely blocking access ofuncertified users.

The control unit 117 transmits a wake-up signal to the BIOS 121 of themain system 12 and the power managing apparatus 122 when it is confirmedthat the user is a legitimate user by the user certifying unit 116. Thepower managing apparatus 122 which receives the wake-up signal providesnormal power to each part of the main system, and the BIOS 121 whichreceives the wake-up call starts to boot up. The control unit 117transmits the IP address stored in the storing unit 1 to the main system12, which is woken up by the wake-up signal.

In addition, the control unit 117 receives the IP address and the MACaddress from the main system 12 and the legacy network card 13 andstores them in the storing unit 115, even when the main system 12 is ina normal state. This enables the main system wake-up apparatus 11 totake the role of the link layer and the network layer of the main system12 and the network card 13. Since the MAC address, which is a physicaladdress, is fixed as long as the legacy network card 13 is not replaced,it only has to be stored once in the storing unit 115. In the case ofthe IP address, a fixed IP address needs only to be stored once in thestoring unit 115, but each new dynamic IP address has to be stored inthe storing unit 15 whenever the main system 12 goes into a sleepingstate.

FIG. 4 is a diagram of a structure of a first example of a communicationsystem according to an embodiment of the present invention.

Referring to FIG. 4, the first communication system includes a remoteterminal 41 and a host 42. The remote terminal 41 can be a PC such as PC1 illustrated in FIG. 2 and has a fixed certified IP address. On theother hand, the host 42 is a general computer having communicationfunctions.

The remote terminal in a sleeping state receives a wake-up request fromthe host 42 to wake up the remote terminal. The destination IP address,which is included in the wake-up request received by the remote terminal41, is the IP address of the remote terminal 41, and the sender IPaddress is the IP address of the host 42. Here and below, the IP addressmay be recorded as a certified IP address or a standard IP address.

The remote terminal 41 which is in a sleeping state certifies whetherthe user of the host 2, which has transmitted the wake-up request, is alegitimate user of the remote terminal 41 based on the informationincluded in the remote request. The wake-up request can be realized asthe wake-up packets 31 and 32 of FIG. 3, and the information included inthe wake-up request refers to the user certification information. Thesame is applied below.

The remote terminal 41 in a sleeping state wakes up by going through theprocess of booting up when the user of the host 42 is certified to be alegitimate user. The remote terminal 42, which is woken up, communicateswith the host 42 using the IP address of the host 2 which is included inthe wake-up request.

The host 42 transmits a wake-up request to the remote terminal 41 whichis in a sleeping state to wake up the remote terminal 1 using the IPaddress of the remote terminal 41, and communicates with the remoteterminal 41 which is woken up by the wake-up request.

FIG. 5 is a flowchart illustrating a first example of a communicationmethod according to an embodiment of the present invention. The firstcommunication method may be carried out by the first communicationsystem of FIG. 4 and is, for ease of explanation only, described inconjunction with FIG. 4. Thus, it is to be understood that the methodmay be performed by other systems. Although not described in FIG. 6, themethod can also be applied to FIG. 5.

Referring to FIGS. 4 and 5, in operation 51 the host 42 transmits awake-up request to the remote terminal 41 which is in a sleeping state,to wake up the remote terminal 41. In operation 52 the remote terminal41 certifies whether the user of the host 42, which has transmitted thewake-up request, is a legitimate user of the remote terminal 41. Inoperation 53, if the user is confirmed to be a legitimate user inoperation 52, the remote terminal 41 is woken up. In operation 54, theremote terminal 41, which is woken up, communicates with the host 42.

FIG. 6 is a flowchart of a method of waking up a main system accordingto an embodiment of the present invention. The method of waking up thefirst main system may be carried out by the PC 1 shown in FIG. 2, and bythe remote terminal 41 shown in FIG. 4. Thus, the method of FIG. 6 isexplained in conjunction with those figures. However, it is to beunderstood that other components may perform the method of FIG. 6.Although not illustrated in FIG. 6, the above description can be appliedto the method of FIG. 6.

Referring to FIGS. 2, 4, and 6, in operation 61 a packet is receivedfrom the host 42 via the network. In operation 62, it is confirmedwhether the main system 12 is in a sleeping state or in a normal state.In operation 63, the received packet is transmitted to the legacynetwork card 13, when it is confirmed that the main system 12 is in anormal state in operation 62.

In operation 64 it is confirmed whether the destination MAC addressincluded in the received packet and the MAC address stored in thestoring unit match, when it is confirmed that the main system 12 is in asleeping state in operation 62. When the destination MAC addressincluded in the received packet is the broadcast address it is confirmedthat the two addresses match. In operation 65, when the two addressesare confirmed as matching in operation 64, it is confirmed whether thedestination IP address included in the received packet matches the IPaddress stored in the storing unit 115. When the destination IP addressincluded in the received packet is the broadcast address, the twoaddresses are confirmed to match.

In operation 66, when the addresses are confirmed as matching, it isconfirmed whether the received packet is a wake-up request. When thepacket is confirmed as being a wake-up request, the security of thesecurity application region included in the received packet is cancelledin operation 67. In operation 68, the user certification information isextracted from the security application region in which security iscancelled, and it is confirmed whether the user of the host 2, which hastransmitted the packet, is a legitimate user of the main system 12 basedon the extracted user certification information. In operation 69, whenthe user is confirmed to be a legitimate user in operation 68, a wake-upsignal is transmitted to the BIOS 121 of the main system 12 and thepower managing apparatus 122. In operation 610, the sender IP addressincluded in the wake-up request, that is, the IP address of the host 2,is transmitted to the protocol stack 123 of the main system 12 which hasbeen woken up. The main system 12 can continue to communicate with thehost 2, through communication with the main system wake-up apparatus 11,by using the IP address of the host 2 transmitted from the main systemwake-up apparatus 11.

FIG. 7 is a diagram of the structure of a second example of acommunication system according to an embodiment of the presentinvention.

Referring to FIG. 7, the second communication system includes a remoteterminal 71, a host 72, a proxy 73, and a dynamic host configurationprotocol (DHCP) server 74. The remote terminal 71 may be realized as aPC 1 shown in FIG. 2 and especially has a dynamic certified IP address.On the other hand, the host 72 is a general computer havingcommunication functions.

The remote terminal 71 in a sleeping state requests an IP address fromthe DHCP server 74 when the rent period of the IP address ends. Theremote terminal 71 in a sleeping state receives a response whichincludes an IP address from the DHCP server 74, which has received therequest. The remote terminal 71 in a sleeping state registers its own IPaddress with the proxy 73.

The remote terminal 71 in a sleeping state receives a wake-up requestform the host 72 to wake up the remote terminal. The remote terminal 71in a sleeping state certifies whether the user of the host 72 whichtransmitted the wake-up request is a legitimate user of the remoteterminal 71 based on the information included in the wake-up request.The remote terminal 71 in a sleeping state wakes up by booting up whenthe user of the host 72 is confirmed to be a legitimate user. The remoteterminal 71 communicates with the host 72 using the IP address of thehost 72 included in the wake-up request.

The DHCP server 74 transmits a response including an IP address to theremote terminal 71 when receiving an IP address request from the remoteterminal 71.

The proxy 73 stores the IP address registered by the remote terminal 71.The proxy 73 transmits a response including the IP address of the remoteterminal 71 to the host 72 when receiving the IP address request of theremote terminal 1 from the host 72.

The host 72 requests the IP address of the remote terminal 71 from theproxy 73 that retains the IP address of the remote terminal 71. The host72 receives a response including the IP address from the proxy 73 whichhas received the request. The host 72 transmits a wake-up request to theremote terminal 71 to wake up the remote terminal 71 using the IPaddress included in the received response. The host 72 communicates withthe remote terminal 71, which has been woken up by the wake-up request.

FIG. 8 is a flowchart of a second communication method according to anembodiment of the present invention. The second communication method maybe carried out by the second communication system shown in FIG. 7 andis, for ease of explanation only, described in conjunction with thatfigure. However, it is to be understood that the method of FIG. 8 can beperformed by other methods. Although not described in FIG. 8, the abovedescription can be applied to the method of FIG. 8.

Referring to FIGS. 7 and 8, in operation 81 the remote terminal 71 in asleeping state requests the DHCP server 74 an IP address. In operation82 the DHCP server 74, which has received the IP address request,transmits the IP address to the remote terminal 71. In operation 83 theremote terminal 71, which has received the IP address, registers thereceived IP address with the proxy 73.

In operation 84 the host 72 requests the proxy 73, which retains the IPaddress that is registered in operation 83 or the IP address that isalready registered, the IP address of the remote terminal 71. Inoperation 85 the proxy 73, which has received the IP address request,transmits a response including the IP address of the remote terminal 71to the host 72.

In operation 86 the host 72, which has received the response from theremote terminal 71, transmits a wake-up request to the remote terminal71 in a sleeping state using the IP address included in the receivedresponse. In operation 87, the remote terminal 71 confirms whether theuser of the host 72, which has transmitted the wake-up request, is alegitimate user of the remote terminal 71. In operation 88, if the useris confirmed as a legitimate user in operation 87, the remote terminal71 is woken up. In operation 89 the remote terminal 71, which is wokenup, communicates with the host 72.

FIG. 9 is a flowchart illustrating a method of waking up a main systemwhen a packet is transmitted according to an embodiment of the presentinvention.

Referring to FIG. 9, the method of waking up the main system when apacket is transmitted includes the following operations. The method ofwaking up the second main system may be carried out by the PC 1 shown inFIG. 2 and the remote terminal 1 shown in FIG. 7. Thus, the method ofFIG. 9 is explained in conjunction with those figures. However, it is tobe understood that other components may perform the method of FIG. 9.Although not illustrated in FIG. 9, the above description can be appliedto the method of FIG. 9.

Referring to FIGS. 2, 7, and 9, in operation 91, it is confirmed whetherthe main system 71 is in a sleeping state or a normal state. Inoperation 92 it is confirmed whether the lending term of the IP addressstored in the storing unit 115 has ended, if it is confirmed that themain system 12 is in a sleeping state. In operation 93, the IP addressis requested from the DHCP server 4, when the lending term is confirmedto have ended.

FIG. 10 is a flowchart of a method of waking up the main system when apacket is received according to an embodiment of the present invention.

Referring to FIG. 10, the method of waking up the main system when apacket is received includes the following operations. The method ofwaking up the main system may carried out by the PC 1 shown in FIG. 2and the remote terminal 1 shown in FIG. 7. Thus, the method of FIG. 10is explained in conjunction with those figures. However, it is to beunderstood that other components may perform the method of FIG. 10.Although not illustrated in FIG. 10, the above description can beapplied to the method of FIG. 10.

Referring to FIGS. 2, 7, and 10, in operation 101, a packet is receivedfrom the host 72 via the network. In operation 102 it is confirmedwhether the main system 12 is in a sleeping state or in a normal state.In operation 103 the received packet is transmitted to the legacynetwork card 13, if the main system 12 is confirmed as being in a normalstate.

In operation 104, if it is confirmed that the main system 12 is in asleeping state, it is checked whether the MAC address included in thereceived packet matches the MAC address stored in the storing unit 115.When the MAC address included in the received packet is the broadcastaddress, it is confirmed that the two addresses match. In operation 105,if the two addresses are confirmed as matching in operation 104, it isconfirmed whether the IP address included in the received packet matchesthe IP address stored in the storing unit 115. When the IP addressincluded in the received packet is the broadcast address, it isconfirmed that the two addresses match.

In operation 106, if the two addresses match in operation 105, it isconfirmed whether the received packet is a response to the IP addressrequest. In operation 107, if the received packet is confirmed as beinga response to the IP address request, the IP address stored in thestoring unit 115 is updated to an IP address included in the response,and the IP address included in the response is registered with the proxy3.

In operation 108, if it is confirmed that the received packet is not aresponse to the IP address request in operation 104, it is confirmedwhether the received packet is a wake-up request. In operation 109, ifthe received packet is confirmed as being a wake-up request in operation108, the security of the security application region included in thereceived packet is cancelled. In operation 1010, the user certificationinformation is extracted from the security application region in whichthe security is cancelled in operation 109, and it is confirmed whetherthe user of the host 2, which has transmitted the packet, is alegitimate user of the main system 12 based on the extracted usercertification information. In operation 1010, if the user is confirmedas being a legitimate user in operation 109, a wake-up signal istransmitted to the BIOS 121 of the main system 12 and the power managingapparatus 122. In operation 1011, a sender IP address which is includedin the wake-up request, that is, the IP address of the host 2, and theIP address updated in operation 105, are transmitted to the protocolstack 123 of the main system 12 which is woken up by the wake-up calltransmitted in operation 1010.

The main system 12 can continue to communicate with the host 2, which iscommunicating with the main system wake-up apparatus by using the IPaddress of the host 2 transmitted from the main system wake-up apparatus11, and updating its own IP address to a new IP address transmitted fromthe main system wake-up apparatus 11.

FIG. 11 is a diagram illustrating a structure of a third example of acommunication system according to an embodiment of the presentinvention.

Referring to FIG. 11, the third communication system includes a remoteterminal 51, a host 52, a proxy 53, a DHCP server 54, and a networkaddress translation (NAT) 55. The remote terminal 51 can be realized asa PC such as PC 1 shown in FIG. 2 and can have a dynamic private IPaddress. On the other hand, the host 52 is a general computer havingcommunication capabilities.

The remote terminal 51 in a sleeping state requests a private IP addressfrom the DHCP server 54 via the NAT 55, when the lending term of its ownprivate IP address ends. The remote terminal 51 in a sleeping statereceives a response including the private IP address from the DHCPserver 54, which has received the request via the NAT 55. The remoteterminal 51 in a sleeping state registers the IP address with the proxy3 via the NAT 55. The IP address, which is registered with the proxy 53,is a certified IP address converted from the private IP address of theremote terminal 51 by the NAT 55.

The remote terminal 51 in a sleeping state transmits a packet to theproxy 53 to maintain the connection with the proxy 53 via the NAT 55, orreceives a packet from the proxy 53 via the NAT 55 to maintain theconnection with the remote terminal 51. The NAT 54 has a NAT table,which maps the private IP address to the certified IP address one toone, and when a private IP address is not used for a certain period,that is, when the NAT mapping term for the private IP address ends, theprivate IP address is deleted from the NAT table. Therefore, the remoteterminal 51 and/or the proxy 53 has to exchange empty packets with theproxy 53 to maintain the connection with the proxy 53, that is to retainthe relevant mapping.

The remote terminal 51 in a sleeping state receives a request forcommunication with the remote terminal 51 which is relayed by the proxy53 via the NAT 55. The communication request includes the IP address ofthe host 52, which has transmitted the communication request. The remoteterminal 51 in a sleeping state transmits a response including its ownIP address to the host 52 via the NAT 55 using the IP address of thehost 52 included in the communication request.

The remote terminal 51 in a sleeping state receives a wake-up requestfrom the host 52 to wake up the remote terminal 51. The remote terminal51 in a sleeping state certifies whether the user of the host 52 whichtransmitted the wake-up request is a legitimate user of the remoteterminal 51 based on information included in the wake-up request. Theremote terminal 1 in a sleeping state is woken up by booting up when itis certified that the user of the host 2 is a legitimate user. Theremote terminal 51, which is woken up, communicates with the host 2using the IP address of the host 52 that is included in the wake-uprequest.

The DHCP server 54 transmits a response including an IP address to theremote terminal 51 via the NAT 55 when receiving the IP address requestfrom the remote terminal 51 via the NAT 55.

The NAT 55 converts the private IP address included in the packet to acertified IP address when the remote terminal 51 transmits the host 52or the proxy 53 existing in a public network and converts the certifiedIP address included in the packet into a private IP address when thehost 52 or the proxy 53 transmits a packet to the remote terminal 51existing in a private network.

The proxy 53 stores the IP address registered by the remote terminal 51via the NAT 55. The proxy 53 transmits a packet to the remote terminal51 via the NAT 55 to maintain the connection with the remote terminal51, or receives a packet to maintain the connection with the proxy 53from the remote terminal 51 via the NAT 55. The proxy 53 relays acommunication request to the remote terminal 51 via the NAT 55 whenreceiving a request for communication with the remote terminal 51 fromthe host 52.

The host 52 requests communication with the remote terminal from theproxy 52. The host 52 receives a response including the IP address ofthe remote terminal 51, from the remote terminal 52 via the NAT 55. Thehost 52 transmits a wake-up request to the remote terminal 51 to wake upthe remote terminal 51 using the IP address included in the receivedresponse. The host 52 communicates with the remote terminal 51 which iswoken up by the wake-up request.

FIG. 12 is a flowchart of a third example of a communication methodaccording to an embodiment of the present invention. The thirdcommunication method may be carried out in the third communicationsystem of FIG. 11 and is, for ease of explanation only, described inconnection with that figure. However, it is to be understood that themethod of FIG. 12 may be performed by other systems. Although notillustrated in FIG. 12, the above description can be applied to themethod of FIG. 12.

Referring to FIGS. 11 and 12, in operation 121 the remote terminal 51,which is in a sleeping state, requests the IP address to the DHCP server54 via the NAT 55. In operation 121, if the IP address is requested, theDHCP server 54, which receives the IP address request, transmits the IPaddress to the remote terminal 51 via the NAT 55. In operation 123 theremote terminal 51, which has received the IP address, registers thereceived IP address with the proxy 3.

In operation 124, the connection between the remote terminal 51 and theproxy 53, which retains the IP address registered in operation 123 or anIP address that has already been registered, is maintained. In operation125, the host requests the proxy 53 communication with the remoteterminal 51 to the proxy 3 which maintains a connection with the remoteterminal 51. In operation 126, the proxy 3, which receives the requestfor communication with the remote terminal 51, relays a communicationrequest to the remote terminal 51 via the NAT 55.

In operation 127, the remote terminal 51, which receives thecommunication request relayed by the proxy 53, transmits a responseincluding its own IP address to the host 52 via the NAT 5. In operation128, the host 52, which receives the response transmitted from theremote terminal 51 via the NAT 55, transmits a wake-up request to theremote terminal 51 In a sleeping state via the NAT 55 to wake up theremote terminal 51 using the IP address included in the receivedresponse. In operation 129, the remote terminal 51 certifies whether theuser of the host 52, which receives the wake-up request, is a legitimateuser of the remote terminal 51. In operation 1210, if the user iscertified to be a legitimate user in operation 129, the remote terminal51 is woken up. In operation 1211, the remote terminal 51, which hasbeen woken up, communicates with the host 52 via the NAT 55.

FIG. 13 is a flowchart of a method of waking up a main system accordingto an embodiment of the present invention when a packet is transmitted.The method of waking up a third main system may be carried out by the PC1 shown in FIG. 2 and the remote terminal 51 shown in FIG. 11. Thus, forease of explanation only the method of FIG. 13 is described withreference to FIGS. 2 and 11. However, it is to be understood that othercomponents may perform the method. Although not illustrated in FIG. 13,the above description can be applied to the method of FIG. 13.

Referring to FIGS. 2, 11, and 13, in operation 131 it is confirmedwhether the main system 2 is in a sleeping state or a normal state. Inoperation 132, if the main system 12 is confirmed to be in a sleepingstate, it is confirmed whether a lending term of the IP address storedin the storing unit 115 has ended. In operation 133, if it is confirmedthat the lending term has ended, the IP address is requested from theDHCP server 54 via the NAT 55. In operation 134, if it is confirmed thatthe lending term has not ended, it is confirmed whether the NAT mappingperiod has ended. In operation 135, if it is confirmed that the lendingterm has ended, a packet is transmitted to the proxy 53 via the NAT 55to maintain the connection with the proxy 53.

FIG. 14 is a flowchart illustrating a method of waking up a main systemaccording to an embodiment of the present invention when a packetreceived. The method of waking up the third system may be carried out bythe PC 1 shown in FIG. 2 and the remote terminal 51 shown in FIG. 11.Thus, for ease of explanation only the method of FIG. 14 is describedwith reference to FIGS. 2 and 11. However, it is to be understood thatother components may perform the method. Although not illustrated inFIG. 14, the above description can be applied to the method of FIG. 14.

Referring to FIGS. 2, 11, and 14, in operation 141 a packet is receivedfrom the host 52 via the network. In operation 142, it is confirmedwhether the main system 12 is in a sleeping state or a normal state. Inoperation 143, if the main system 12 is confirmed to be in a normalstate in operation 142, the received packet is transmitted to the legacynetwork card 13.

In operation 144, if the main system 12 is confirmed as being in asleeping state, it is confirmed whether the MAC address included in thereceived packet matches the MAC address stored in the storing unit 115.When the MAC address included in the received packet is a broadcastaddress the two are confirmed as matching. In operation 145, if the twoaddresses are confirmed as matching it is confirmed whether the IPaddress included in the received packet matches the IP address stored inthe storing unit 115. When the IP address of the received packet is abroadcast address the two are confirmed as matching.

In operation 146, if the two addresses are confirmed as matching inoperation 145, it is confirmed whether the received packet is a responseto the IP address request. In operation 147, if the received packet isconfirmed to be a response to the IP address request in operation 146,the IP address stored in the storing unit 115 is updated to the IPaddress included in the response, and the IP address included in theresponse is registered with the proxy 53.

In operation 148, if it is confirmed that the received packet is not aresponse to the IP address request, it is confirmed whether the receivedpacket is a packet for maintaining the connection with the proxy 53. Inoperation 149, if it is confirmed that the packet is for maintaining theconnection with the proxy 3 in operation 148, a NAT mapping period forthe IP address stored in the storing unit is initialized.

In operation 1410, if it is confirmed that the packet is not formaintaining the connection with the proxy 53 in operation 148, it isconfirmed whether the received packet is a request for communicationwith the remote terminal 51. In operation 1411, if the received packetis confirmed to be a request for communication with the remote terminal51, a response including the IP address of the remote terminal 51 istransmitted to the host 52 which transmitted the communication request.

In operation 1412, if it is confirmed that the received packet is not arequest for communication with the remote terminal 51 in operation 1410,it is confirmed whether the received packet is a wake-up request. Inoperation 1413, if the received packet is confirmed to be a wake uprequest in operation 1412, the security of the security applicationregion included in the received packet is cancelled. In operation 1414,user certification information is extracted from the securityapplication region in which the security is cancelled in operation 1413,and it is confirmed whether the user of the host 52 which transmittedthe packet is a legitimate user of the main system 12 based on theextracted user certification information. In operation 1415, if the useris confirmed as being a legitimate user in operation 1414, a wake-upsignal is transmitted to the BIOS 121 of the main system 12 and thepower managing apparatus 122. In operation 1416, a sender IP addressincluded in a wake-up request, that is, the IP address of the host 52,and an IP address updated in operation 105 are transmitted to theprotocol stack 123 of the main system 12 which is woken up by thewake-up signal transmitted in operation 1415.

The main system 12 can continue to communicate with the host 52 whichcommunicates with the main system wake-up apparatus 11 by using the IPaddress of the host 52 transmitted from the main system wake-upapparatus 11 and updating its own IP address to a new IP addresstransmitted from the main system wake-up apparatus 11.

The above-described embodiments of the present invention can be realizedas code on a recording medium readable by a computer. These computerreadable media include, but are not limited to, storage media such asmagnetic storage media (e.g., ROM's, floppy disks, hard disks, etc.),and optically readable media (e.g., CD-ROMs, DVDs, etc).

According to the above-described embodiments of the present invention,access of an uncertified user is prevented by carrying out usercertification of the process of logging on or logging in to the mainsystem before the main system wakes up. Furthermore, the possibility ofa malicious user retrieving information stored in the PC or damaging theremote terminal is completely eliminated by performing usercertification based on user certification information secured when themain system is in a sleeping state.

In addition, according to the above-described embodiments of the presentinvention, additional services can be provided by including higher layerinformation as well as the link layer in the wake-up packet to wake upthe main system, and providing the received higher layer informationwhich continuously changes to the main system which is woken up. Themain system can continuously communicate with the terminal which is in asleeping state by using the higher layer information. In other words,the wake-up packet can be received through an optimum pathway using therouting service provided by the router by including the IP address inthe wake-up packet and provide the dynamic IP address to the mainsystem.

Although a few embodiments of the present invention have been shown anddescribed, the present invention is not limited to the describedembodiments. Instead, it would be appreciated by those skilled in theart that changes may be made to these embodiments without departing fromthe principles and spirit of the invention, the scope of which isdefined by the claims and their equivalents.

1. A method of waking up a main system, comprising: receiving a packet;confirming whether the received packet is a response to internetprotocol (IP) address request from a dynamic host configuration protocol(DHCP) server; confirming whether the received packet is a request forwaking up a main system in a sleeping state, from a host; certifyingwhether a user of the host is a legitimate user of the main system, ifthe received packet is the waking up request from the host, not theresponse from the DHCP server; and transmitting a wake-up signal to themain system when it is certified that the user is legitimate, wherein ifthe host has the medium access control (MAC) address of the main systemand does not have internet protocol (IP) address of the main system, thepacket includes the MAC address of the main system and IP broadcastaddress, and wherein if the host does not have the MAC address of themain system and has the IP address of the main system, the packetincludes MAC broadcast address and the IP address of the main system. 2.The method of claim 1, wherein the certifying is based on informationfor logging on or logging in to the main system.
 3. The method of claim1, further comprising: canceling security of a security applicationregion included in the packet; and extracting information on certifyinga user from the security application region, wherein the certifying isbased on the extracted information.
 4. The method of claim 1, whereinthe confirming is on the basis of higher layer information included inthe packet, wherein the certifying is performed when the received packetis confirmed to be the wake-up request, and the higher layer informationis information of layers at least as high as a network layer.
 5. Anapparatus for waking up a main system, comprising: a receiving unitwhich receives a packet; a processing unit which confirms whether thereceived packet is a response to internet protocol (IP) address requestfrom a dynamic host configuration protocol (DHCP) server, and confirmswhether the received packet is a request for waking up a main system ina sleeping state, from a host; a certifying unit which certifies whethera user of the host is a legitimate user, if the received packet is thewaking up request from the host, not the response from the DHCP server;and a control unit which transmits a drive signal to the main systemwhen the certifying unit confirms that the user is a legitimate user,wherein if the host has the medium access control (MAC) address of themain system and does not have internet protocol (IP) address of the mainsystem, the packet includes the MAC address of the main system and IPbroadcast address, and wherein if the host does not have the MAC addressof the main system and has the IP address of the main system, the packetincludes MAC broadcast address and the IP address of the main system. 6.The apparatus of claim 5, wherein the user certifying unit performs thecertification based on information for logging on or logging in to themain system.
 7. The apparatus of claim 5, further comprising: a securityengine which cancels security of a security application region includedin the packet, wherein the processing unit extracts information on usercertification from the security application region, wherein the usercertifying unit performs the certification based on information on usercertification extracted by the processing unit.
 8. The apparatus ofclaim 5, wherein the processing unit confirms based on higher layerinformation included in the packet, wherein the user certifying unitperforms the certification when the processing unit confirms that thereceived packet is the waking up request, and the higher layerinformation is information of layers at least as high as a networklayer.
 9. A method of transmitting higher layer information from a host,comprising: receiving a packet from the host; confirming whether thereceived packet is a response to internet protocol (IP) address requestfrom a dynamic host configuration protocol (DHCP) server; confirmingwhether the received packet is a request for waking up a main system ina sleeping state, from a host; and transmitting the higher layerinformation included in the received packet, to the main system that iswoken up by the packet, if the received packet is the waking up requestfrom the host, not the response from the DHCP server, wherein the higherlayer information is information of layers at least as high as a networklayer, wherein if the host has the medium access control (MAC) addressof the main system and does not have internet protocol (IP) address ofthe main system, the packet includes the MAC address of the main systemand IP broadcast address, and wherein if the host does not have the MACaddress of the main system and has the IP address of the main system,the packet includes MAC broadcast address and the IP address of the mainsystem.
 10. The method of claim 9, wherein the higher layer informationis a dynamic IP address.
 11. The method of claim 9, further comprisingreceiving a packet which has passed a determined optimum network pathwaybased on the higher layer information.
 12. The method of claim 11,wherein the higher layer information is an IP address, and in thereceiving, a packet which passes along an optimum network pathwaydetermined by a router based on the IP address is received.
 13. Acommunication method comprising: receiving a packet from a host;confirming whether the received packet is a response to internetprotocol (IP) address request from a dynamic host configuration protocol(DHCP) server; confirming whether the received packet is a request forwaking up a remote terminal in a sleeping state, from a host; certifyingwhether a user of the host is a legitimate user of the remote terminal,if the received packet is the waking up request from the host, not theresponse from the DHCP server; waking up the remote terminal when it isconfirmed that the user is a legitimate user; and communicating betweenthe host and the remote terminal which is woken up, wherein if the hosthas the medium access control (MAC) address of the remote terminal anddoes not have internet protocol (IP) address of the remote terminal, thepacket includes the MAC address of the remote terminal and the IPbroadcast address, and wherein if the host does not have the MAC addressof the remote terminal and has the IP address of the remote terminal,the packet includes MAC broadcast address and the IP address of theremote terminal.
 14. The method of claim 13, further comprising:transmitting the dynamic address to the host via a proxy which retainsthe dynamic address of the remote terminal, wherein, in the requesting,transmission is performed using the dynamic address received in thetransmitting.
 15. The method of claim 14, further comprising:registering the dynamic address to the proxy via the remote terminal;and requesting via the host the address of the remote terminal from theproxy which retains the registered dynamic address, wherein, in thetransmitting, a response including the dynamic address is transmittedalong with the request transmitted the requesting via the host theaddress.
 16. The method of claim 13, further comprising transmitting viathe remote terminal the dynamic address of the remote terminal to thehost, wherein, the host requests the waking up of the remote terminalusing the dynamic address transmitted in the transmitting.
 17. Themethod of claim 16, further comprising: registering via the remoteterminal the dynamic address to the proxy; transmitting from the hostthe request for communication with the remote terminal to the proxywhich retains the registered dynamic address registered; and receivingvia the proxy the transmitted communication request and relaying thecommunication request to the remote terminal, wherein, in thetransmitting the dynamic address, a response including the dynamicaddress is transmitted along with the communication request relayed inthe receiving via the proxy.
 18. A computer readable medium encoded withprocessing instructions for causing a processor to perform a method ofwaking up a main system, the method comprising: receiving a packet froma host; confirming whether the received packet is a response to internetprotocol (IP) address request from a dynamic host configuration protocol(DHCP) server; confirming whether the received packet is a request forwaking up a main system in a sleeping state, from the host; certifyingwhether a user of the host is a legitimate user, if the received packetis the waking up request from the host, not the response from the DHCPserver; and transmitting a wake-up signal to the main system when it iscertified that the user is a legitimate user, wherein if the host hasthe medium access control (MAC) address of the main system and does nothave internet protocol (IP) address of the main system, the packetincludes the MAC address of the main system and IP broadcast address,and wherein if the host does not have the MAC address of the main systemand has the IP address of the main system, the packet includes MACbroadcast address and the IP address of the main system.
 19. A computerreadable medium encoded with processing instructions for causing aprocessor to perform a method of transmitting higher layer information,the method comprising: receiving a packet from a host; confirmingwhether the received packet is a response to internet protocol (IP)address request from a dynamic host configuration protocol (DHCP)server; confirming whether the received packet is a request for wakingup a main system in a sleeping state, from the host; and transmittingthe stored higher layer information included in the received packet, tothe main system which is woken up by the packet, if the received packetis the waking up request from the host, not the response from the DHCPserver, wherein the higher layer information is information of layers atleast the same level as a network layer, wherein if the host has themedium access control (MAC) address of the main system and does not haveinternet protocol (IP) address of the main system, the packet includesthe MAC address of the main system and IP broadcast address, and whereinif the host does not have the MAC address of the main system and has theIP address of the main system, the packet includes MAC broadcast addressand the IP address of the main system.
 20. A computer readable mediumencoded with processing instructions for causing a processor to performa communication method, the method comprising: receiving a packet;confirming whether the received packet is a response to internetprotocol (IP) address request from a dynamic host configuration protocol(DHCP) server; confirming whether the received packet is a request forwaking up a main system in a sleeping state, from a host; certifyingwhether a user of the host is a legitimate user of the remote terminalresponding to the request, if the received packet is the waking uprequest from the host, not the response form the DHCP server; waking upthe remote terminal when it is confirmed that the user is a legitimateuser; and communicating between the host and the remote terminal whichis woken up, wherein if the host has the medium access control (MAC)address of the remote terminal and does not have internet protocol (IP)address of the remote terminal, the packet includes the MAC address ofthe remote terminal and IP broadcast address, and wherein if the hostsystem does not have the MAC address of the remote terminal and has theIP address of the remote terminal, the packet includes MAC broadcastaddress and the IP address of the remote terminal.